With the development of the semiconductor industry, three-dimensional (3D) semiconductor devices are getting more attractive due to their increased storage capability. In a 3D memory device, a source is generally routed using interconnection layers including source contacts. Some memory devices may include source contacts inside memory arrays. However, a large number of source contacts in a memory array of a memory device may degrade the efficiency of the memory array and result in a large die size and a high fabrication cost.